JOHN H. WELSH 185 



WELSH: But when you looked at other parts, you found that the 

 tentacles were richer than the body wall? 



ROSS: A bit, but on the borderline. 



LENHOFF: Couldn't we view the tetramethylammonium com- 

 pounds not as toxins, but as part of the normal nervous system trans- 

 mitters of coelenterates since tetramine is present in all of the tis- 

 sues assayed? I ask this question because when glutathione activates 

 the feeding response in H. littoralis, some of the few substances 

 that enhance the response are certain tetramethylammonium com- 

 pounds. Possibly the transmission of the glutathione stimulus goes 

 through a tetramine-mediated pathway rather than through an 

 acetylchloline-mediated pathway? 



WELSH: I think it is entirely possible. We have no evidence on 

 the tetramine one way or the other. However, tetramine does occur 

 in a number of venoms; it occurs in the salivary glands of some 

 marine gastropods in large amounts. And, of course, other choline 

 esters, and other quaternary ammonium compounds occur in certain 

 molluscs. But that tetramine may be taking the place of acetylcho- 

 line in the coelenterate nervous system is a good possibility. 



HESS: Do these animals have choline esterase or acetylcholine? 



WELSH: There is choline esterase. 



PASSANO: I suspect that the acetylcholine esterase system is 

 not significant in the functioning of the scyphozoan nervous sys- 

 tem, and we know that 5-hydroxytryptamine also fails to have 

 any effect. Could it be that the use of these substances, toxic to 

 other animals as nematocyst toxins, might be valuable to the 

 coelenterates because they would avoid the danger of self-inHicted 

 paralysis? Is this even why their neuropharmacology is different 

 from that of other animals? 



WELSH: Venomous animals are generally successful in keeping 

 their venoms away from themselves. 



PASSANO: Well I would like to ask then, in other people^s 

 experience in studying the feeding responses of nematocyst-bear- 

 ing animals, are the nematocysts always prevented from penetrating 



